Hubble Space Telescope
The Hubble Space Telescope is the visible/ultraviolet/near-infrared element of the Great Observatories astronomical program. The spacecraft provides an order of magnitude better resolution than is capable from ground-based telescopes. The objectives of the HST are to:
1) Investigate the composition, physical characteristics, and dynamics of celestial bodies; 2) Examine the formation, structure, and evolution of stars and galaxies; 3) Study the history and evolution of the universe; 4) Provide a long-term space-based research facility for optical astronomy.
During initial on-orbit checkout of the Hubble's systems, a flaw in the telescope's main reflective mirror was found that prevented perfect focus of the incoming light. This flaw was caused by the incorrect adjustment of a testing device used in building the mirror. Fortunately, however, Hubble was designed for regular on-orbit maintenance by Shuttle missions. The first servicing mission, STS-61 in December 1993, fully corrected the problem by installing a corrective optics package and upgraded instruments (as well as replacing other satellite components). A second servicing mission, scheduled for March 1997, installed two new instruments in the observatory.